In order to curb peak power demand, time period-based electricity billing plans, demand response (DR), and other such demand adjustment methods are known. As specific methods for adjusting demand, a technique in which a power company (electric utility) requests that power customers curb power consumption and pays customers an incentive (also called a reward or a rebate) relative to the amount of power saved, and a technique in which power supply and demand are adjusted by controlling a distributed generation system so as to resolve the difference between the aggregate power demand and the aggregate power supply, are known (for example, Patent Literature 1, 2).
In demand response, a power company contracts with the customer to save power before a tight power supply situation occurs. In this contract, the power company proposes to the customer a requested amount of power savings and offers a rate discount when the request is agreed to. The power company also checks whether or not the customer implemented power savings in accordance with the contract by measuring the customer's usage after power has become tight.